unit 5 - educlash
TRANSCRIPT
Unit 5.1
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UNIT 5CHAPTER 1
DATAWAREHOUSING
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1.ETL: Transformations and OtherOperators:
STORE mapping,Adding source and target operators,AddingTransformation Operators, Using a Key Lookupoperator, Creating an external table, Creating and loading alookup table, Retrieving the key to use for a LookupOperator,Adding a Key Lookup operator, PRODUCTmapping, SALES cube mapping, Dimension attributes in thecube, Measures and other attributes in the cube, Mappingvalues to cube attributes, Mapping measures' values to acube, Mapping PRODUCT and STORE dimension values tothe cube, Mapping DATE_DIM values to the cube, Featuresand benefits of OWB.
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STORE mapping In the Design Center, we will right-click on the Mappings
node of the ACME_DW_PROJECT | Databases |Oracle | ACME_DWH database and select New.... EnterSTORE_MAP
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Adding source and targetoperators
Use POS_TRANS_STAGE table as our source table. The target for this mapping is going to be the STORE
dimension
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connect the following attributestogether:
STORE_NAME to NAME STORE_NUMBER to STORE_NUMBER STORE_ADDRESS1 toADDRESS1 STORE_ADDRESS2 toADDRESS2 STORE_CITY to CITY STORE_STATE to STATE STORE_ZIPPOSTALCODE to ZIP_POSTALCODE STORE_REGION to REGION_NAME
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STORE_NAME, STORE_NUMBER:We need to trim spacesand change these attributes to uppercase to facilitate queriesas they are part of the business identifier STORE_ADDRESS1, ADDRESS2, CITY, STATE, and
ZIP_POSTALCODE:We need to trim spaces and change theSTATE attribute to uppercase STORE_REGION:We need to trim spaces and change this
attribute to uppercase
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Adding TransformationOperators
The particular transformationnames we need under the characterheading are the upper() function toconvert to uppercase and the trim()function to remove whitespace.
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After dropping theTransformationOperator on themapping, it will pop upa dialog box where weselect thetransformation wewant to use.
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After making all these connections, our mapping should now looksimilar to the following with all the Transformation Operators
collapsed into their icon views:
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step2
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Using a Key Lookup operator
Key Lookup operators, as the name implies, are used forlooking up information from other sources based on somekey attribute(s) in a mapping.
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Creating an external table an external table's data is stored in a flat file that is external to the
database. External tables are created under the Oracle | ACME_DWH |
External Tables node in the Design Center, so we'll right-clickon it and select New... from the pop-up menu. This will launchthe ExternalTable wizard Step 1.We'll name this external table COUNTIES Step 2. select the file that contains the metadata for the
external table (COUNTIES_CSV ) Step 3. will select the default location to use for this table .
The drop-down menu on this screen will display the filelocations that have been defined in the Design Center.Wewill select the ACME_FILES_LOCATION entry, which is forthe files that exist for this project.
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Creating and loading a lookup table we have our source table defined for our new lookup table let's create a
new mapping called COUNTIES_LOOKUP_MAP using the samemethod we've used previously 1. Right-click on the Mappings node, select New..., enter
COUNTIES_LOOKUP_MAP in the name field, and click on the OKbutton.
2. In the Mapping Editor that pops up, let's drag an ExternalTable Operatorfrom the Palette window onto the mapping.
3. On the Add External Table Operator pop-up window that appears, ourCOUNTIES external table is visible.We will select that and click on the OKbutton to continue.This will drop an External Table Operator on ourmapping that is bound to our COUNTIES external table.
4.We need to get that data loaded into a regular table in the database, sonext we'll drag aTable Operator onto the mapping.
5. In the resulting AddTable Operator pop up that appears, we specify whattable we want to add.
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We'll click on OKand it will drop aTable Operator ontoour mapping with noattributes defined init.
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Let's drag a line from the output group (OUTGRP1) of ourCOUNTIES external table over to the input/output group(INOUTGRP1) of our new COUNTIES_LOOKUP table. This mapping is done. However, there is one more step we
need to take to actually create the lookup table definition.Remember we created our table operator as an unboundoperator, which means it's not associated with any databaseobject. If we look in the ACME_DWH |Tables node, there isno
table named COUNTIES_LOOKUP.
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1. When we right-click on the unbounded operator, the pop-upmenu has a menu selection called Create and Bind....Withthis option we will create a new table object in the OWB
Tables node and bind this operator to it.
2. The name is the same as what we gave to the operator.3. The Create in: text field is to specify the module in which to
create the new table under our project in the Design Center.4. When we click on the OK button on this dialog box, a table is
created in theTables node and is bound to theoperator.
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When we use the option to create a table in this manner, it creates abasic, no-frills table with no constraints defined on it.To add a primary
key, we'll perform the following steps:
1.In the Design Center, open the COUNTIES_LOOKUP table in the DataObject Editor by double-clicking on it under the Tablesnode.
2. Click on the Constraints tab.3. Click on the Add Constraint button.4.Type PK_COUNTIES_LOOKUP (or any other naming convention we
might choose) in the Name column.5.In theType column, click on the drop-down menu and select Primary
Key.6.Click on the Local Columns column, and then click on the AddLocal
Column button.7. Click on the drop-down menu that appears and select the ID column.8. Close the Data Object Editor.
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Retrieving the key to use for a LookupOperator
The county ID is only a portion of the entire STORE_NUMBERfield, so we can't just use the STORE_NUMBER from input as thedirect key to a Key Lookup Operator.
actually a fixed known format, and the positions three through sixof the number are actually the code for the location of the store inthe county.
The county ID is only a portion of the entire STORE_NUMBERfield, so we can't just use the STORE_NUMBER from input as thedirect key to a Key Lookup Operator.We will have to extract theID number out of it and then convert it to a number before wecan use it to look up the county.
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Adding a SUBSTR TransformationOperator
TheTransformation Operators available to us in OWB include aSUBSTR (or substring) transformation that will do exactly whatwe need to extract the county ID value out of theSTORE_NUMBER field.
The SUBSTR transformation takes three parameters—the stringwe want to extract the substring from, a number indicating thestart position of the substring within the string, and a numberindicating the length of the substring to extract.
drag aTransformation Operator onto theSTORE_MAP mappingbetween the POS_TRANS_STAGE table and the STOREdimension below all the otherTransformationOperators.
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Adding a Constant operator We'll click and drag a Constant operator onto the mapping
to the left of the SUBSTR Transformation Operator. We can see that it has an output group called OUTGRP1
by default. We'll right-click on it and select Open Details... from the
pop-up menu.
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Clicking on the Output Attributes tab we see that thereare no attributes currently existing for this operator. This is where we will add our constants that we need for the
SUBSTR operator. OUTPUT1 We'll change the name to position.
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Adding a TO_NUMBERtransformation
The SUBSTR value is ready and we can use it to look up thecounty ID, but there's one more transformation we need toapply before we can use it to look up the county name. it needs to be converted into a number to match the data
type of the ID field in the COUNTIES_LOOKUP table Todo this, we will use the TO_NUMBER() function. let's drag a Transformation Operator onto our mapping
to the right of the SUBSTR operator and selectTO_NUMBER from the resulting pop up.
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Adding a Key Lookup operator After that little side trip to quickly create our lookup table
and add a SUBSTR operator with a TO_NUMBERtransformation to convert the result to a number. Let's drag a Key Lookup operator onto the mapping and
drop it to the right of the TO_NUMBER operator. the KEY_LOOKUPWizard is launched
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1. Rename it to COUNTIES_LOOKUP2. Key Lookup operators require one input and one output
group (INGRP1 and OUTGRP1 )3. select one or more operators to map into the input group
of the Key Lookup operator
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Step 3
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4. will specify in which object to look up the value.Wewill click onthe Next button toproceed to the finalstep where we willspecify what toreturn if no recordis found in thelookup table.
So we'll click on NULL that currently appears as the default for the COUNTY_NAME value andtype in 'UNKNOWN' in the box.
Wewill click on the Next button to proceed to the Summary screen
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Now we have a completed mappingthat will populate our STORE
dimension
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PRODUCT mapping The mapping for the PRODUCT dimension will be similar
to the STORE mapping
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SALES cube mapping drag each of these onto our mapping usingTable Operator forthe
POS_TRANS_STAGE table and Cube Operator for the SALEScube.
The POS_TRANS_STAGE table is very familiar to us as we haveused it for the two dimensions, but the SALES cube is new. Itlooks slightly different than the dimensions we worked withearlier .
For the STORE dimension, we identified NAME andSTORE_NUMBER as the business identifiers.
The third dimension we have defined for our cube is theDATE_DIM dimension.
Toopen it in the Data Object Editor, navigate in the DesignCenter to ACME_DWH | Dimensions |DATE_DIM anddouble-click to open it.
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look at the Levels tab where we can inspect each level of the dimension and seewhat attributes were identified for each level.We can scroll down and click on theDAY level
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Mapping an Expression operator(fordate)
Wecan launch the Expression Builder byclicking on the button with three dots to theright of the Expression input field thatappeared when we clicked on it.TheExpression Builder dialog box appears andwe can create our expression.
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Features and benefits of OWB By providing us the ROLAP option, the OracleWarehouse
Builder opens to us the design features of cubes anddimensions even though we'll be implementing themrelationally with tables in our database. The Expression Builder provides us a powerful tool
to use for interactively building expressions. Support for Slowly Changing Dimensions is built in
with the Enterprise ETL option.
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UNIT 5END OF CHAPTER 1
DATAWAREHOUSING
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